Which statement about G protein-coupled receptors (GPCRs) is accurate?

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Hormones attach directly to G proteins located on the cell membrane.For G protein activation, the alpha, beta, and gamma subunits must remain connected.The alpha subunit variation causes G proteins to have either inhibitory or stimulatory effects.In their inactive form, G proteins are bound to GTP.G proteins function independently of any nucleotide binding.

Explanation

G proteins can either inhibit or stimulate cellular responses depending on the type of alpha subunit they contain, which determines their functional role. Contrary to some misconceptions, hormones do not bind directly to G proteins but to the receptors, and the G protein is bound to GDP, not GTP, in its resting state. Also, the alpha subunit dissociates from beta and gamma subunits upon activation.